Fuel delivery control based on estimated fuel temperature

Abstract

In one embodiment of the present invention, a method for estimating temperature of fuel in a fuel delivery system of a motor vehicle engine includes the step of calculating a fuel temperature estimate in an engine running state as a function of fuel flow rate, engine coolant temperature and intake air temperature. In a second embodiment of the present invention, a method for estimating temperature of fuel in a fuel delivery system of a motor vehicle engine includes the step of calculating a fuel temperature estimate in an engine not running state as a function of a fuel temperature estimate when the engine was last in a running state, time the engine has been in the not running state, engine coolant temperature and intake air temperature.

What is claimed is: 
     
       1. A method for controlling fuel delivery in a fuel delivery system of a motor vehicle engines said method comprising the steps of: calculating a fuel temperature estimate in an engine running state in accordance with fuel flow rate, engine coolant temperature and intake air temperature to said engine; and   modifying said fuel delivery in view of said fuel temperature estimate in an engine running state.   
     
     
       2. A method for controlling fuel delivery in a fuel delivery system of a motor vehicle engine, said method comprising the steps of: calculating a fuel temperature estimate in an engine running state as a function of fuel flow rate, engine coolant temperature and intake air temperature to said engine; and   modifying said fuel delivery in view of said fuel temperature estimate in an engine running state;   wherein said step of calculating a fuel temperature estimate in an engine running state further comprises the step of calculating an average of intake air temperature and engine coolant temperature.   
     
     
       3. A method as recited in claim 2, wherein said step of calculating a fuel temperature estimate in an engine running state further comprises the steps of: determining a factor which is a function of fuel flow rate into said engine; and   calculating a steady-state fuel temperature approximation as a function of actual or inferred ambient temperature in the vicinity of said vehicle, said factor and said average of intake air temperature and engine coolant temperature.   
     
     
       4. A method as recited in claim 3, wherein said steady-state fuel temperature approximation is calculated as:   FT.sub.-- SS=FT.sub.-- MUL*(FT.sub.-- FORC-AMB.sub.-- TEMP)+AMB.sub.-- TEMP;     wherein FT --  SS is said steady-state fuel temperature approximation, FT --  FORC is said average of engine coolant temperature and intake air temperature, AMB --  TEMP is said actual or inferred ambient temperature, FT --  MUL is said factor; and   FT --  MUL decreases with increasing fuel flow rate.   
     
     
       5. A method as recited in claim 3, wherein said step of calculating a fuel temperature estimate in an engine running state further comprises the step of applying a lag function to said steady-state fuel temperature approximation to obtain a fuel temperature estimate. 
     
     
       6. A method as recited in claim 5, wherein said step of applying a lag function further comprises the step of using a time constant which is a function of fuel flow rate into said engine. 
     
     
       7. A method as recited in claim 5, wherein said step of applying a lag function further comprises the step of using a time constant which is a function of air flow rate into said engine. 
     
     
       8. A method as recited in claim 4, wherein said step of calculating a fuel temperature estimate in an engine running state further comprises the step of applying a lag function to said steady-state fuel temperature approximation FT --  SS to obtain a fuel temperature estimate FT. 
     
     
       9. A method as recited in claim 8, wherein said step of applying a lag function further comprises the step of using a time constant which is a function of fuel flow rate into said engine. 
     
     
       10. A method as recited in claim 8, wherein said step of applying a lag function further comprises the step of using a time constant which is a function of air flow rate into said engine. 
     
     
       11. A method as recited in claim 2, wherein said step of calculating a fuel temperature estimate in an engine running state further comprise the steps of: determining a factor which is a function of fuel flow rate into said engine; and   calculating a steady-state fuel temperature approximation as a function of actual or inferred temperature of fuel in said fuel tank, said factor and said average of intake air temperature and engine coolant temperature.   
     
     
       12. A method recited in claim 11, wherein: inferred temperature of fuel in said fuel tank is used in calculating said steady-state fuel temperature approximation; and   actual or inferred ambient temperature in the vicinity of said vehicle is used as said inferred temperature of fuel in said fuel tank.   
     
     
       13. A method for controlling fuel delivery in a fuel delivery system of a motor vehicle engine, said method comprising the steps of: calculating a fuel temperature estimate in an engine running state as a function of fuel-flow rate, engine coolant temperature and intake air temperature to said engine;   modifying said fuel delivery in view of said fuel temperature estimate in an engine running state; and   calculating a fuel temperature estimate in an engine not running state as a function of a fuel temperature estimate when said engine was last in a running state, time said engine has been in said not running state, engine coolant temperature and intake air temperature.   
     
     
       14. A method as recited in claim 13, wherein said step of calculating a fuel temperature estimate in an engine not running state further comprises the steps of: calculating an average of engine coolant temperature and intake air temperature;   calculating said fuel temperature estimate in an engine not running state as:   FT=FT.sub.-- FORC+e.sup.-(SOAK.sbsp.--.sup.TMR/TC.sbsp.--.sup.FT.sbsp.--.sup.SOAK) *(FT.sub.-- KO-FT.sub.-- FORC),     where FT is said fuel temperature estimate in an engine not running state, FT --  FORC is said average of engine coolant temperature and intake air temperature, SOAK --  TMR is said time that said engine has been in said not running state, TC --  FT --  SOAK is a time constant, and FT --  KO is said fuel temperature estimate when said engine was last running.     
     
     
       15. A digital memory device adapted to direct a microcomputer to estimate temperature of fuel in a fuel delivery system of a motor vehicle engine, said digital memory device comprising: means for directing a microcomputer to calculate an average of engine coolant temperature and engine intake air temperature;   means for directing a microcomputer to determine a factor as a function of fuel flow rate;   means for directing a microcomputer to determine a steady-state fuel temperature approximation in an engine running condition as:   FT.sub.-- SS=FT.sub.-- MUL*(FT.sub.-- FORC-AMB.sub.-- TEMP)+AMB.sub.-- TEMP,     wherein FT --  SS is said steady-state fuel temperature approximation, FT --  MUL is said factor, FT --  FORC is said weighted average of engine coolant temperature and engine intake air temperature, and AMB --  TEMP is an inferred ambient temperature.     
     
     
       16. A digital memory device as recited in claim 15, further comprising: means for directing a microcomputer to calculate a second average of engine coolant temperature and engine in take air temperature;   means for directing a microcomputer to calculate a fuel temperature estimate in an engine not running state as:   FT=FT.sub.-- FORC+e.sup.-(SOAK.sbsp.--.sup.TMR/TC.sbsp.--.sup.FT.sbsp.--.sup.SOAK) *(FT.sub.-- KO-FT.sub.-- FORC),     where FT is said fuel temperature estimate in an engine not running state, FT --  FORC is said second average of engine coolant temperature and engine intake air temperature, SOAK --  TMR is a time that said engine has been in said not running state, TC --  FT --  SOAK is a time constant, and FT --  KO is a fuel temperature estimate when said engine was last running.